The foraging behavior of Worm-eating Warblers (Helmitheros vermivorus) was studied in Maryland during the breeding season and in Jamaica, Dominican Republic, and Belize during the nonbreeding season. Over 75% of the foraging maneuvers recorded from May to early August in Maryland were directed towards live foliage, whereas over 75% of the maneuvers were directed towards dead curled leaves in the understory of tropical forest in the temperate zone winter. Sampling of the relative abundance of arthropods associated with dead and live foliage showed that although the ratio of total numbers in dead and live leaves was similar in the temperate and tropical sites, the overall ratio of estimated biomass was considerably greater in the tropical sites. This is because large arthropods commonly use dead curled leaves as daytime roosts in tropical forests. However, the largest temperatezone arthropods are generally found on leaf surfaces during the day. The winter-foraging specialization on dead leaf arthropods apparently is the more demanding; the most specialized search and attack behaviors are associated with feeding at dead and live curled leaves. I revisited the Belize study sites in September, when Worm-eating Warblers were presumably arriving and found an intermediate use of dead and live leaves. Relative abundances of arthropods on dead and live leaves were similar to those found in the winter period at the same sites. This suggests a period of transition which is consistent with the trial and error learning hypothesis for the development of seasonal foraging specializations in this species.